(a) Field of the Invention
The present invention relates to a high-resolution, modular gamma or X-ray camera based on a scintillator and an image intensifier having a strong optical gain that are optically coupled to a solid state detector.
(b) Brief Description of the Related Art
In the field of single photon emission computed tomography (SPECT) and molecular imaging, gamma-ray detectors with high spatial resolution are used. Currently, the high-resolution requirement for such systems can be satisfied by using a gamma-ray detector based on high-speed and low-noise charge coupled devices (CCD). Such detectors yield a spatial resolution that is sufficient to satisfy the high-resolution measurement requirements. In these detectors, a scintillation flash is observed as a cluster of signal spread over multiple pixels of the CCD. A few varieties of such detectors exist and each requires the use of a low-noise, high-quantum-efficiency CCD to observe the scintillation events. Such detectors typically consist of thin scintillators optically coupled to an expensive Electron-Multiplying CCD imager (EMCCD) where charge gain is applied within the CCD pixels. A fiber-optic taper that increases the field of view can be used to increase the active imaging area but at the expense of light intensity, thus making cluster detection difficult as well as imposing a limitation of the usable thickness of the scintillation crystal for gamma-ray detection.
Another system utilizes a scintillator attached to an electrostatic demagnifying tube (DM) which provides slight gain and an increase in the active imaging area, but light loss in the system requires coupling to an EMCCD via a fiber-optic taper to compensate for the losses. Another CCD-based gamma-ray detector is capable of imaging individual gamma-ray interactions using a high-efficiency optical configuration and a low-noise, high-quantum efficiency, cooled CCD imagers. Substantial disadvantages of this system are that it only works with relatively thin scintillators that are less sensitive, and the CCD used for the detection must be configured to use long readout time for reduced noise which greatly reduces the frame rate capability of the system.
Despite all of the above mentioned improvements in the field of gamma-ray detection as discussed above, there is a strong need for increased sensitivity and read-out frequency of the measured scintillations to detect gamma-ray sources for many different applications, such as small-animal SPECT and molecular imaging. Advances in systems are therefore strongly desired requiring high-resolution, high-speed, and highly-sensitive gamma-ray detectors, without substantially increasing the costs of such a system.